The present invention relates to a semiconductor rectifier arrangement. More particularly the present invention relates to such a rectifier arrangement in which two unencapsulated rectifier elements, each having at least one pn-junction, are each fastened, via a respective metallic contact disc and in a manner that insulates the rectifier elements electrically and provides good heat conductance, on a common cooling member provided with means for the passage of a coolant, in which each rectifier element is connected at its upper connecting terminal to another rectifier element via a conductor member fastened on the contact disc of the other rectifier element to form an antiparallel circuit, and in which the structure including the cooling member, rectifier elements and current conducting members is embedded in an insulating mass.
It is known that controllable semiconductor devices called thyristors can be switched from the nonconducting to the conducting state at any desired time during the halfwave charging them in the forward direction by a pulse applied to their control electrode. Such controllable semiconductor devices thus constitute contactless switches. Due to this advantageous property and other known advantages, thyristors are increasingly used to switch and control high currents, for example in the welding art, e.g., in antiparallel circuits as so-called a.c. control elements.
In such known devices, disc-shaped thyristors are provided with cooling elements for liquid cooling which provide a space-saving structure and high current handling capability. The assembly of such arrangements is complicated, however, because the above-mentioned thyristor structures require a cooling element at each of the two contact surfaces in order to approximately uniformly dissipate the power loss heat to both sides, and because the cooling elements must be assembled so that they are electrically insulated against one another. The hoses provided for the inlet and outflow of the coolant, tap water is preferred for this purpose, between the cooling elements of such known arrangements have a considerable length due to the different potentials of the cooling elements and the not negligible conductance of the coolant. With an alternating terminal voltage of 500 V.sub.eff, an operating temperature of the coolant of about 60.degree. C, and with the requirement that the heat loss produced in the coolant acting as a parallel resistance in the hoses may be only a few Watt, the use of tap water results in a hose length between the cooling elements of about 50 cm.
Embodiments have now been proposed in which the housing part supporting an unencapsulated rectifier element is simultaneously designed as a cooling element so as to optimize the power loss heat dissipation and is provided with a channel in its interior for the passage of coolant so that the coolant is conducted past the rectifier element at the shortest possible distance. While this does improve the operating behavior of such rectifier arrangements, the drawbacks of the thus required long external coolant lines are still present.
Structures have also been proposed in which the cooling member carrying the rectifier elements is provided with a cavity in its interior serving as a channel for the passage of coolant, and the coolant channel is formed by recesses in a base or lid portion of the two-piece cooling member or by suitably arranged partitions in a hollow body cooling member. It has been proposed, inter alia, to provide the coolant channel in a massive ceramic cover member. However, tests have shown that heat dissipation in such structures is in no way optimum.